The present invention relates to an engine balancer for a vehicle, such as an automobile, which can effectively reduce vibration that is caused in the engine. More specifically, the present invention relates to an engine balancer which can effectively reduce gear rattle noise that is caused by mutually meshing teeth of a drive gear and a driven gear of the engine balancer during operation of the engine.
Japanese Patent Application First Publication No. 2000-65150 discloses an engine balancer for an automobile which is disposed within an oil pan below a cylinder block of the engine. The engine balancer includes a casing fixed to a lower portion of the cylinder block and a pair of balance shafts disposed parallel to each other within the casing. The balance shafts, namely, a drive balance shaft and a driven balance shaft, are rotatably supported at journals which are disposed on front-end and rear-end portions of the respective balance shafts. The drive balance shaft has an axial length longer than that of the driven balance shaft. The drive balance shaft has balance weights on the rear side portion and a drive gear on the front end portion. The balance weights and the drive gear are integrally formed with the drive balance shaft. A sprocket is disposed on the front end portion of the drive balance shaft. The sprocket is connected with a sprocket disposed on a distal end portion of the crankshaft through a chain which is wound around the sprockets. The drive balance shaft is rotationally driven by a crankshaft via the chain. The driven balance shaft has balance weights on the rear side portion and a driven gear on the front side portion. The driven gear is meshed with the drive gear and transmits the rotation of the drive balance shaft to the driven balance shaft. An oil pump is arranged on the rear end portion of the driven balance shaft. When the crankshaft is rotationally driven at the start of the engine operation, the drive balance shaft with the drive gear is rotated at a speed twice crankshaft speed in one direction. The rotation of the drive gear is transmitted to the driven gear so that the driven balance shaft is rotated in a direction opposite to the one direction through the meshing engagement of the driven gear with the drive gear. The respective balance weights on the drive and the driven balance shafts are rotated and effectively suppress a second order vibration.